Represents an annotated element of the program currently running in this
VM. This interface allows annotations to be read reflectively. All
annotations returned by methods in this interface are immutable and
serializable. The arrays returned by methods of this interface may be modified
by callers without affecting the arrays returned to other callers.

Android note: methods that return multiple annotations of different types such as
getAnnotations() and getDeclaredAnnotations() can be affected
by the explicit character-code ordering of annotations types specified by the DEX format.
Annotations of different types on a single element are not guaranteed to be returned in the order
they are declared in source.

The getAnnotationsByType(Class) and getDeclaredAnnotationsByType(Class) methods support multiple
annotations of the same type on an element. If the argument to
either method is a repeatable annotation type (JLS 9.6), then the
method will "look through" a container annotation (JLS 9.7), if
present, and return any annotations inside the container. Container
annotations may be generated at compile-time to wrap multiple
annotations of the argument type.

The terms directly present, indirectly present,
present, and associated are used throughout this
interface to describe precisely which annotations are returned by
methods:

An annotation A is directly present on an
element E if E is annotated by A in the original source.

An annotation A is indirectly present on an
element E if E is annotated by a container annotation
of A.

An annotation A is present on an element E if either:

A is directly present on E; or

No annotation of A 's type is directly present on
E, and E is a class, and A 's type is
inheritable, and A is present on the superclass of E.

An annotation A is associated with an element E
if either:

A is directly or indirectly present on E; or

No annotation of A 's type is directly or indirectly
present on E, and E is a class, and A's type
is inheritable, and A is associated with the superclass of
E.

The table below summarizes which kind of annotation presence
different methods in this interface examine.

Overview of kind of presence detected by different AnnotatedElement methods

For an invocation of get[Declared]AnnotationsByType( Class <
T >), the order of annotations which are directly or indirectly
present on an element E is computed as if indirectly present
annotations on E are directly present on E in place
of their container annotation, in the order in which they appear in
the value element of the container annotation.

There are several compatibility concerns to keep in mind if an
annotation type T is originally not repeatable and
later modified to be repeatable.
The containing annotation type for T is TC.

Modifying T to be repeatable is source and binary
compatible with existing uses of T and with existing uses
of TC.
That is, for source compatibility, source code with annotations of
type T or of type TC will still compile. For binary
compatibility, class files with annotations of type T or of
type TC (or with other kinds of uses of type T or of
type TC) will link against the modified version of T
if they linked against the earlier version.
(An annotation type TC may informally serve as an acting
containing annotation type before T is modified to be
formally repeatable. Alternatively, when T is made
repeatable, TC can be introduced as a new type.)

If an annotation type TC is present on an element, and
T is modified to be repeatable with TC as its
containing annotation type then:

The change to T is behaviorally compatible with respect
to the get[Declared]Annotation(Class<T>) (called with an
argument of T or TC) and get[Declared]Annotations() methods because the results of the
methods will not change due to TC becoming the containing
annotation type for T.

The change to T changes the results of the get[Declared]AnnotationsByType(Class<T>) methods called with an
argument of T, because those methods will now recognize an
annotation of type TC as a container annotation for T
and will "look through" it to expose annotations of type T.

If an annotation of type T is present on an
element and T is made repeatable and more annotations of
type T are added to the element:

The addition of the annotations of type T is both
source compatible and binary compatible.

The addition of the annotations of type T changes the results
of the get[Declared]Annotation(Class<T>) methods and get[Declared]Annotations() methods, because those methods will now
only see a container annotation on the element and not see an
annotation of type T.

The addition of the annotations of type T changes the
results of the get[Declared]AnnotationsByType(Class<T>)
methods, because their results will expose the additional
annotations of type T whereas previously they exposed only a
single annotation of type T.

If an annotation returned by a method in this interface contains
(directly or indirectly) a Class-valued member referring to
a class that is not accessible in this VM, attempting to read the class
by calling the relevant Class-returning method on the returned annotation
will result in a TypeNotPresentException.

Similarly, attempting to read an enum-valued member will result in
a EnumConstantNotPresentException if the enum constant in the
annotation is no longer present in the enum type.

If an annotation type T is (meta-)annotated with an
@Repeatable annotation whose value element indicates a type
TC, but TC does not declare a value() method
with a return type of T[], then an exception of type
AnnotationFormatError is thrown.

getAnnotations

Returns annotations that are present on this element.
If there are no annotations present on this element, the return
value is an array of length 0.
The caller of this method is free to modify the returned array; it will
have no effect on the arrays returned to other callers.

getAnnotationsByType

Returns annotations that are associated with this element.
If there are no annotations associated with this element, the return
value is an array of length 0.
The difference between this method and getAnnotation(Class)
is that this method detects if its argument is a repeatable
annotation type (JLS 9.6), and if so, attempts to find one or
more annotations of that type by "looking through" a container
annotation.
The caller of this method is free to modify the returned array; it will
have no effect on the arrays returned to other callers.

Implementation Requirements:

The default implementation first calls getDeclaredAnnotationsByType(Class) passing annotationClass as the argument. If the returned array has
length greater than zero, the array is returned. If the returned
array is zero-length and this AnnotatedElement is a
class and the argument type is an inheritable annotation type,
and the superclass of this AnnotatedElement is non-null,
then the returned result is the result of calling getAnnotationsByType(Class) on the superclass with annotationClass as the argument. Otherwise, a zero-length
array is returned.

Parameters

annotationClass

Class: the Class object corresponding to the
annotation type

Returns

T[]

all this element's annotations for the specified annotation type if
associated with this element, else an array of length zero

getDeclaredAnnotation

Returns this element's annotation for the specified type if
such an annotation is directly present, else null.
This method ignores inherited annotations. (Returns null if no
annotations are directly present on this element.)

Implementation Requirements:

The default implementation first performs a null check
and then loops over the results of getDeclaredAnnotations() returning the first annotation whose
annotation type matches the argument type.

Parameters

annotationClass

Class: the Class object corresponding to the
annotation type

Returns

T

this element's annotation for the specified annotation type if
directly present on this element, else null

getDeclaredAnnotations

Returns annotations that are directly present on this element.
This method ignores inherited annotations.
If there are no annotations directly present on this element,
the return value is an array of length 0.
The caller of this method is free to modify the returned array; it will
have no effect on the arrays returned to other callers.

getDeclaredAnnotationsByType

Returns this element's annotation(s) for the specified type if
such annotations are either directly present or
indirectly present. This method ignores inherited
annotations.
If there are no specified annotations directly or indirectly
present on this element, the return value is an array of length
0.
The difference between this method and getDeclaredAnnotation(Class) is that this method detects if its
argument is a repeatable annotation type (JLS 9.6), and if so,
attempts to find one or more annotations of that type by "looking
through" a container annotation if one is present.
The caller of this method is free to modify the returned array; it will
have no effect on the arrays returned to other callers.

Implementation Requirements:

The default implementation may call getDeclaredAnnotation(Class) one or more times to find a
directly present annotation and, if the annotation type is
repeatable, to find a container annotation. If annotations of
the annotation type annotationClass are found to be both
directly and indirectly present, then getDeclaredAnnotations() will get called to determine the
order of the elements in the returned array.